Some multi-band or other tactical radios operate in the high frequency (HF), very high frequency (VHF) (for satellite communications), and ultra high frequency (UHF) bands. The range of these multi-band tactical radios can operate over about 2 through about 512 MHz frequency range. Next generation radios will probably cover about 2.0 to about 2,000 MHz (or higher) to accommodate high data rate waveforms and less crowded frequency bands. This high frequency transmit mode is governed by standards such as MIL-STD-188-141B, while data modulation/demodulation is governed by standards such as MIL-STD-188-110B, the disclosures which are incorporated by reference in their entirety.
UHF standards, on the other hand, provide different challenges over the 225 to about 512 MHz frequency range, including short-haul line-of-sight (LOS) communication and satellite communications (SATCOM) and cable. This type of propagation can be obtained through different weather conditions, foliage and other obstacles making UHF SATCOM an indispensable communications medium for many agencies. Different directional antennas can be used to improve antenna gain and improve data rates on the transmit and receive links. This type of communication is typically governed in one example by MIL-STD-188-181B, the disclosure which is incorporated by reference in its entirety. This standard specifies a family of constant and non-constant amplitude waveforms for use over satellite links.
The joint tactical radio system (JTRS) implements some of these standards and has different designs that use oscillators, mixers, switchers, splitters, combiners and power amplifier devices to cover different frequency ranges. The modulation schemes used for these types of systems can occupy a fixed bandwidth channel at a fixed carrier frequency or can be frequency-hopped. These systems usually utilize memoryless modulations, such as a phase shift keying (PSK), amplitude shift keying (ASK), frequency shift keying (FSK), quadrature amplitude modulation (QAM), or modulations with memory such as continuous phase modulation (CPM) and combine them with a convolutional or other type of forward error correction code.
These systems often use a number of base station segments that are operative with HF and VHF communications nets and often ad-hoc communications networks in which a plurality of N mobile radios are located on a terrain, typically each moving with no fixed infrastructure. The ad-hoc networks typically require data communications and mobile voice and video that are cheap and reliable. There are different channel access schemes available, but often, there are problems with hidden terminals and some channel access mechanisms use a request-to-send (RTS) and a clear-to-send (CTS) approach to make communication more efficient. In this type of mechanism the channel access is typically receiver directed and uses complex state machines. It behaves similar to Carrier Sense Multiple Access (CSMA), but does not work for broadcast. Other channel access mechanisms may use a time slot approach. These mechanisms are transmitter directed and have good features of Time Division Multiple Access (TDMA), but often require synchronized clocks and a distributed algorithm. There would usually be some delay versus throughput tradeoff in different routing protocols such as a link state (SPF) or distance vector or on-demand routing protocols, and it can be optimized by caching, pruning or source routing. Sometimes there are hierarchical ad-hoc networks, using some degree of power control, and hierarchical link-state routing, and RTS/CPS wave forms.
Power efficient and covert communications systems typically require minimizing the amount of power transmitted in order to reduce the total power expenditure and minimize the probability that users will be detected. Some prior art techniques of adapting power within infrastructure-less networks, e.g., ad-hoc networks, for example, use periodic beacons to inform other users that power levels would use a request/response technique where all users in the communications network are required to respond to the request. The beacon technique requires the communications network to be continually transmitting information and as a result, either energy is expanded or the transmitter is more readily detected. In a request/response network, the complete communication network is transmitting in response to a request, thus expending unnecessary energy or increasing the probability of detection.